As fresh water supply becomes a major issue in many parts of the world, wastewater treatment that can allow water reuse is set to gain popularity, the research found. However, at present many countries still lack the resources and the infrastructure to treat wastewater. Less than a third of the 181 countries studied had records on the three key aspects of wastewater -- generation, treatment and reuse. A similar proportion had no record on any of these, the study showed.

In North America, the annual amount of water treated is equivalent to the volume of the water flowing over Niagara Falls but only four percent of it is reused. Overall, 85 cubic km of wastewater is generated in North America every year, with about 61 cubic km of this actually treated. Close to half of all reclaimed water in states like California and Florida is used for irrigation, data shows.

According to UNU-INWEH director Zafar Adeel, if wastewater treatment is properly done it could have an enormous economic value. For example, treating wastewater can cut costs for fertilizer production because nutrients such as potash, nitrogen and phosphorus could be extracted in the treatment process, the study said.